Revenue Recognition (Narrative) (Details) - USD ($)	1 Months Ended	3 Months Ended
	Dec. 31, 2018	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Contract asset associated with revenues from contracts with customers		$ 0
Contract liability associated with revenues from contracts with customers		$ 0
Minimum | NGL sales
Disaggregation of Revenue [Line Items]
Payment terms		30 days
Minimum | Marketing
Disaggregation of Revenue [Line Items]
Payment terms		30 days
Minimum | Gas gathering
Disaggregation of Revenue [Line Items]
Payment terms		30 days
Maximum | NGL sales
Disaggregation of Revenue [Line Items]
Payment terms		60 days
Maximum | Marketing
Disaggregation of Revenue [Line Items]
Payment terms		60 days
Maximum | Gas gathering
Disaggregation of Revenue [Line Items]
Payment terms		60 days
Fayetteville Shale
Disaggregation of Revenue [Line Items]
Percentage of assets sold	100.00%